In recent years, highly efficient motors have been demanded along with an increase in awareness of energy saving, and there have been proposed a large number of interior permanent magnet motors using rare-earth magnets having high residual flux density and coercivity in a rotor to realize high efficiency. Further, with structure in which the magnets are embedded in the rotor, a reluctance torque as well as a magnet torque can be used, thereby being capable of constructing the highly efficient motor. The reluctance torque is proportional to a difference in inductance between a d-axis (center axis of the permanent magnet) and a q-axis (axis extending between the adjacent magnets and forming an electrical angle of 90 deg. with respect to the d-axis). Thus, in order to improve the reluctance torque, in general, structure in which a q-axis magnetic flux easily passes therethrough and a d-axis magnetic flux less easily passes therethrough is desired.
For example, in the technology disclosed in Patent Literature 1, a shortest distance of an interval between adjacent flat-plate magnets is set larger than a shortest distance between adjacent side surfaces of teeth. In this manner, a magnetic flux in a q-axis direction is increased to generate a large reluctance torque.
Further, in the technology disclosed in Patent Literature 2, the flat-plate magnets are arranged into V-shapes to generate the reluctance torque.